Flow behaviour of liquid metals on solid substrates

Abstract

The influence of both fluid flow and heat transfer on the shape of a liquid metal pool has been studied by pouring liquid 50%Pb-50%Sn alloy onto a colder stainless steel substrate in air. The liquid alloy does not wet the solid substrate and the shape of the pool is governed principally by the balance of forces due to gravity and surface tension. The momentum of the entering liquid provides an additional force which favours spreading. Inertial forces are significant only in the beginning, when the width of the pool is <10 mm. Viscous forces become important in retarding flow whenever the alloy cools to between the liquidus and solidus temperatures (into the ‘mushy’ zone) because of heat transfer to the cold plate. The flow of liquid alloy over the substrate occurs predominantly by a ‘penetrating’ mechanism, in which fresh liquid is incorporated into the pool at the centre to the full depth and simply displaces the existing mass outwards. Temperature-response measurements tend to confirm that this is the flow mechanism.